The present invention relates to a cylinder head for an internal combustion engine, having a fuel injector therewith associated and particularly to the design of the head for receiving the operating rods of the cylinder head components.
The design of a cylinder head normally involves several compromises between a number of conflicting aims. Several of these are here mentioned. Intake ports are required to be designed with sufficient length to provide suitable intake air control. The intake ports must connect to the combustion chamber with a certain inclination to provide a certain vorticity or swirling in the combustion chamber. The exhaust ports must be designed short enough to avoid the diffusion of heat in the cylinder head. The mounting holes of the cylinder head must be arranged so that they are uniformly distributed to provide even clamping against the engine block. Cooling ducts must be located in the most suitable position. Fuel injectors must be fitted centrally to optimize combustion in the combustion changer. Provision must be made for supplying fuel to the fuel injectors via suitably shaped feed lines. The cylinder head must be manufactured by a suitable production method. One basic problem is that there is a shortage of sufficient space for the required partial solutions within the limited volume of the cylinder head.
In the case of cylinder heads for diesel engines with four valves per cylinder and with separate intake ports these problems are more pronounced. Moreover, if the fuel injector is of the type which is referred to as a "unit injector", it requires a mechanical drive for generating a high injection pressure, and this drive also requires a great deal of space. Normally, such a fuel injector is driven by the engine camshaft in a similar fashion to the valve drive. Where the camshaft is located below the cylinder head, a number of push rods must be arranged between the camshaft and the cylinder head. These push rods must in turn actuate rocker arms on the cylinder head to control the fuel injector and valves. The push rods are normally arranged to pass through the cylinder head via a number of through holes designed for this purpose. Where the cylinder head is of the so-called crossflow type, which means that the intake ports and exhaust ports open out on opposite sides of the cylinder head, the intake and exhaust ports will occupy a large amount of space, causing problems in finding a suitable space for the through holes of the push rods.
U.S. Pat. No. 4,945,873 describes a cylinder head in which the push rods for the intake and exhaust valves are located in the same through hole. There is no push rod for driving the fuel injectors, and there are no further details given on the design of the cylinder head. In order to find space for the intake ports, they are not designed as separate ports but they are combined to form one common port, which is not only common to the intake ports for one cylinder but for two. This makes it necessary to provide a cylinder head which is common to at least two cylinders. In this case it is necessary to sacrifice the design of the intake ports, which is probably not the best design from the flow viewpoint.